Adducts hydroxyl radical

In related work, the reactions of hydrogen peroxide with iron(II) complexes, including Feu(edta), were examined.3 Some experiments were carried out with added 5.5"-dimethyl-1-pyrroline-N-oxide (DMPO) as a trapping reagent fa so-called spin trap) for HO. These experiments were done to learn whether HO was truly as free as it is when generated photochemically. The hydroxyl radical adduct was indeed detected. but for some (not all) iron complexes evidence was obtained for an additional oxidizing intermediate, presumably an oxo-iron complex. 

In principle, EPR spectrometry is well suited as a method to monitor kinetic events however, in practice, the time required to tune the spectrometer, and its intrinsically low sensitivity compared to fluorescence or light-absorption spectrometry, affect its competitiveness. Relatively slow reactions on the timescale of minutes, such as the decomposition of the DMPO-superoxide adduct and the subsequent formation of the hydroxyl radical adduct (cf. Pou et al. 1989) are readily followed, either as the first-order disappearance of the DMPO/ OOH signal... 

Formaldehyde (HCHO) FORM Toluene-hydroxyl radical adduct T02... 

Paraffin carbon bond (C-C) PAR Xylene-hydroxyl radical adduct XINT... 

Klein GW, Bhatia K, Madhavan V, Schuler RH (1975) Reaction of OH with benzoic acid. Isomer distribution in the radical intermediates.) Phys Chem 79 1767-1774 Klein SM, Cohen G, Cederbaum Al (1981) Production of formaldehyde during metabolism of dimethyl sulfoxide by hydroxyl radical generating systems. Biochemistry 20 6006-6012 Kumarathasan P, Vincent R, Goegan P, Potvin M, Guenette J (2001) Hydroxyl radical adduct of 5-aminosalicylic acid a potential marker of ozone-induced oxidative stress. Biochem Cell Biol 79 33-42... 

Bamatraf MMM, O Neill P, Rao BSM (1998) Redox dependence of the rate of interaction of hydroxyl radical adducts of DNA nucleobases with oxidants consequences for DNA strand breakage. J Am Chem Soc 120 11852-11857... 

The strongest evidence for direct hole oxidation as the principal step in the photooxidation step comes from a recent study performed by Draper and Fox that failed to detect any of the expected intermediate hydroxyl radical adducts following diffuse reflectance flash photolysis of several titanium dioxide/substrate combinations [33]. In each case where the product of hydroxyl radical-mediated oxidation was known to be different from that of direct electron transfer oxidation, the authors observed only the products of the direct electron-transfer oxidation. 

Fig. 3.7. First derivative liquid-phase ESR spectra for nitroxide radicals formed by the spin-trapping method, (a) the CC13 adduct of PBN, showing hyperfine coupling to the 14N and H of the parent nitrone (b) the same species formed from l1-CClj radicals, showing the extra large doublet splitting from l3C (The /Mines are from an extraneous radical species.) (c) the hydroxyl radical adduct of DMPO, showing the characteristic 1 2 2 1 quartet, generated because of the fortuitous equality of the 1H and l4N splittings.

Sun L, Hoy AR, Bolton JR (1996) Generation Efficiency of the Hydroxyl Radical Adduct of the DMPO Spin Trap in Homogeneous and Heterogeneous Media, J Adv. Oxid. Technol. 1, No. 1 44—52... 

Repair reactions of hydroxyl radical adducts to the pyrimidine C5-C6 double bonds... 

Zhao C, Shi Y, Wang W, Lin W, Fan B, Jia Z, Yao S, Zheng R. (2002) Fast repair activities of quercetin and rutin toward dCMP hydroxyl radical adducts. Radiat Phys Chem 63 137-142. 

Tomita M, Okuyama T, Watanabe S, Watanabe H. Quantitation of the hydroxyl radical adducts of salicylic acid by micellar elec-trokinetic capillary chromatography oxidizing species formed by a Fenton reaction. Arch Toxicol 1994 68 428-433. 

The number of different hydroxyl radical adducts formed and the rate with which some of these species decompose to the ascorbate radical radical depends upon pH. The decomposition rates for the OH-radical adducts vary from 5 fxs to 1.5 ms (23). Definite structure assignment to the various OH-radical adducts was obtained by ESR studies discussed in the next section. 

Hydroxyl radical, phosphate radical anion, and sulfate radical anion add to the 5 position of oxazole <90JPC1887>. The hydroxyl radical adduct is stable at pH 5-9, but reacts further above or below that range to give a ring-opened product (Scheme 22). 

Figure 7. Formation of hydroxyl radical adduct in N, 0-saturated solution at...

Although tandem lesions were detected from the peroxyl radical (88, Scheme 38) of the C5-hydroxyl radical adduct of thymidine (76) and some were characterized by MS (eg 89, 90, Scheme 38), the reactivity of... 

San Pedro JMN, Greenberg MM. Photochemical generation and reactivity of the major hydroxyl radical adduct of thymidine. Org Lett. 2012 14 2866-2869. 

Electron spin resonance spin trapping analysis of the signals obtained from the perfused rabbit retina showed that hydroxyl radical adducts were generated during the ischaemic period with no further increase at reperfusion (Muller et al. 1997). Electron spin resonance detection of the ascorbyl free radical/dimethyl sulfoxide complex in the retina confirmed that an oxidative stress occurred under ischaemia and was not increased under reperfusion. 

In addition to the hydroxyl radical adducts, exposure of the pyrimidines to hydroxyl radicals is known to lead to a variety of other final reaction products. These will however not be treated here. 

Using the same experimental conditions, we measured hydroxyl radical formation, using radical trap DMPO, for both DHI-melanin and melanoma cells in culture.(25) The con arison was telling for both, addition of CAT decreased the signal, while SOD caused a large increase in the hydroxyl-radical adduct. Our hypothesis is that the pro-oxidant response in both chemical and cell culture studies are due to the pro-oxidant reactivity of melanin. 

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